New answers tagged dsa
Let me first answer your actual question (and then I'll proceed to answer something slightly different that I think will be informative and helpful). Your question asks whether it's possible to use only a DSA key. Technically speaking, this is of course possible. The reason is that a DSA key has exactly the same format as an ElGamal key. No one forces you to ...
Sure you can do. There are many lattice attacks, using your second assumption, to ECDSA (which also applied to DSA). For instance see Smart and Howgrave-Graham and Shparlinski and Nguyen. All the lattice attacks base on finding small solutions (for the ephemeral key $k$ and the private key $a$) to the signing equation $sk-ra\equiv H(m)\pmod q.$ If you have ...
ECDH is not for signing. Your sign method using ecdh does not look like any valid signature scheme I have ever seen, and is therefore likely wildly insecure. Note that the Q&A you link to is asking a very different question.
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